Users can provide inputs to electronic devices using many different approaches. In particular, an electronic device can include one or more types of input interfaces including, for example, a button, switch, slider, touch interface, wheel, or combinations of these. In some cases, an input interface can include one or more dome switches. Using a traditional dome switch, a user can at least partially invert a dome to close an electrical circuit underneath the dome and provide a detectable input. The dome switch is typically constructed by placing a conductive dome over a contact pad on a circuit board. When the dome is pressed, the dome can invert such that the inner surface of the dome contacts the contact pad, and provides a conductive path between the periphery of the dome and the contact pad. The dome inversion can also provide a tactile ‘click’ that enhances the user's interaction with the switch. A user can actuate a dome switch using any suitable approach including, for example, by applying a force directly to the dome, or by pressing a cosmetic component having a nub that is aligned with the dome.
A dome switch can include one or more openings for allowing air to be displaced from underneath the dome when the dome is depressed (e.g., to decrease the air pressure under the dome and provide a desired tactile feedback). For example, a dome switch can include one or more openings in a layer provided over the dome for securing the dome to the circuit board. The openings in the dome switch, however, can provide a path for debris, water, or other external particles or contaminants to enter a volume underneath the dome and around the contact pad. If contaminants infiltrate the volume, the contaminants can cause corrosion or promote the formation of substances that prevent the proper operation of the switch. For example, foreign particles can cause rust, oxidation, dendrite growth, or salt, sugar or chemical deposits. As another example, water can infiltrate the internal volume of the dome switch and short the switch.